The invention concerns a method for the production and recording of nuclear magnetic resonance (NMR) signals in chosen regions of an investigational object, in particular for the production of slice images of a body with which, in an excitation step, a narrow band radio frequency (RF) pulse is irradiated into the investigational object in a homogeneous static magnetic field in the presence of a slice selection gradient G.sub.S in order to produce an NMR signal in a selected slice of the investigational object and with which, in a recording step, the produced NMR signal is read-out in the presence of a read gradient G.sub.R which is perpendicular to the slice selection gradient G.sub.S.
A method of this kind is, for example, known in the art from DE 35 04 734 A1.
The production of nuclear magnetic resonance tomography images with the assistance of a gradient echo sequence is a method frequently used in clinical applications (see also: Higgins Ch, Hricak H, Helms C, Magnetic Resonance Imaging of the Body, Raven Press, New York, 1992, p. 177 ff.). In particular, the application of such a sequence to the investigation of signal changes occurring during activation of cortical areas has recently been shown to be useful (see Frahm, J. et al. Magnetic Resonance in Medicine 29: 139, 1993). Due to the BOLD contrast mechanism used herewith (see Ogawa, Set al. Proc.Natl.Acad.Sci. USA 89:5951, 1992), these investigations require a signal read-out with long echo times of 40-80 ms. Since the repetition time for the recording of sequential individual projection steps must necessarily be larger than the signal read-out time, recording times thereby result of ca. 10-20 s per image for a recording matrix of 128.times.256 to 256.times.256. A shortening of these recording times by about one half can be achieved by so-called echo-shifting, known in the art from Liu G. et al. (Proc.XIIth Annual Meeting SMRM, New York, p. 13, 1993).
It is therefore the purpose of the present invention to present a method of the above-mentioned kind with which the entire recording time can be further substantially reduced.